Floatation module and method

ABSTRACT

An apparatus for reducing the load applied to a rig. The rig is positioned over a well, with the well having a tubular string disposed therein. A landing string is connected to the tubular string such as casing, production and/or testing assemblies. The apparatus comprises a floatation module attached to the landing string and a clamp for clamping the floatation module onto the landing string. In one embodiment, the floatation module comprises a tubular sleeve having a buoyant material applied thereto. The tubular sleeve includes slots. The clamp may contain a set of dies adapted to engage the slots of the tubular sleeve. A method of landing a work string into a sub-sea well head from a floating drilling rig is also disclosed, wherein a marine riser connects the rig to the sub-sea well head.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority from applicationSer. No. 10/946,798, filed Sep. 22, 2004, now issued as U.S. Pat. No.7,383,885.

FIELD OF THE INVENTION

This invention relates to a floatation module and method of using thefloatation module. More particularly, but not by way of limitation, thisinvention relates to a floatation module and method for safely reducingthe rig hoisting requirements to run tubular strings into sub-sea wellsand well bores.

BACKGROUND OF THE INVENTION

As the energy industry continues to search the globe for hydrocarbonreservoirs, the search has increasingly focused in the world's oceans.Economical hydrocarbon reservoirs are increasingly being discovered anddeveloped in deep water tracts located in remote and exotic places onthe planet. Floating drilling platforms, such as mobile offshoredrilling units (MODU's), are anchored in water depths of more than 9,200feet and are dynamically positioned in water depths greater than 10,000feet.

In combination with this deep water drilling, the actual wells drilledare in increasingly deeper water in order to penetrate commerciallyfeasible hydrocarbon reservoirs. Hence, these wells can exceed 34,000feet in depth. The equipment required to safely drill ultra deep waterwells is large, extremely heavy, and difficult to safely handle. Asunderstood by those of ordinary skill in the art, the lifting andlowering capacity of the drilling rigs, including MODU's, are loaded tothe maximum safe working loads.

For instance, if an operator is running a casing string into a well boreto a sub-sea wellhead, the operator is required to lift out of thecasing slips then lower that proper amount of casing. However, theoperator will also be required to pick-up and lower a landing string incombination with the casing, and wherein the ultimate length of thelanding string will be basically equal to the distance between therotary table and sub-sea well head at the sea floor. Therefore, thecombined weight of the casing string and the landing string could pushthe safe hoisting and drill pipe slip's capacity of the MODU to itsmaximum designed safe working loads.

The landing string is specifically designed to provide the very hightensile strengths (now rated to 1,500,000 lbs. working load) to safelyland out casing in the sub-sea well head. As the water depth increases,the length and weights of the landing string increase proportionately.Existing MODU's are now operating at or near their maximum hoistingcapabilities with loads of 1,500,000 to 2,000,000 pounds. Casing loadsof 1,500,000 pounds translate to dynamic loads of 1,750,000 lbs or more(depending on hole condition, fluid characteristics, casing designs,friction) when picking up out of the slips. In some cases, this exposesthe entire load path/hoisting system (top drive, subs, crown sheaves,derrick, slips and brakes) to maximum loading.

Numerous problems involving drill pipe slip crushing and catastrophicslip failures have occurred which have required new heavier designs thateven now barely meet load requirements. Loading the hoisting system tothe maximum of its design creates several safety concerns including, butnot limited to: special landing strings being designed that are heavierwall, which further exacerbates the load handling requirements; righoisting system capability to safely handle extreme loads(static/dynamic); the rig's capability to safely apply over-pull intight hole conditions; the requirement of inspection of hoisting andbraking system prior to the job; and dynamic loads which reach and/orexceed safe working capabilities.

A prior art technique, known as floating, is sometimes used to reducecasing loads during running. The floating technique entails running thecasing without completely filling the entire length with fluid,therefore establishing buoyancy due to the air inside. This presentsseveral concerns for operations, equipment, and the health and safety ofthe rig crew. For instance, some of the problems encountered include:extremely high differential pressures on float equipment; failure offloat equipment could cause immediate overloading of rig hoisting systemcaused by loss of buoyancy, which would be catastrophic; well controland/or stuck pipe due to swabbing or suction if floats fail; casingcollapse; and, removal of air in casing effects circulation andcementation of the casing.

Therefore, there is a need for an apparatus and method for running andlanding casing from floating drilling platforms. There is also a needfor a device and method that can reduce the rig hoisting requirements tosafely run casing strings from floating drilling platforms. These aswell as many other needs will be met by the invention herein disclosed.

SUMMARY OF THE INVENTION

An apparatus for reducing the load applied to a rig. The rig beingpositioned over a well, with the well having a tubular string disposedtherein. A landing string is connected to the tubular string, such ascasing or production equipment. The apparatus comprises a floatationmodule attached to the landing string and a clamp means for clamping thefloatation module onto the landing string. Also included is engagementmeans, located on the floatation module, for engaging with the clampmeans.

In one preferred embodiment, the floatation module comprises a tubularsleeve having buoyant material applied thereto. The engagement meansincludes slots formed in the tubular sleeve. In the most preferredembodiment, the tubular sleeve is constructed of aluminum and thebuoyant material comprises a foam bonded to the aluminum sleeve.

Also in the most preferred embodiment, the tubular sleeve comprises afirst cylindrical half body pivotly attached to a second cylindricalhalf body. The clamp means further includes a first shell attached to asecond shell, and wherein said first shell and said second shell arepivotly attached to form a cylindrical member. The clamp means mayfurther comprise a first set of dies adapted to engage the slot of thefirst tubular.

In one embodiment, a second floatation module is attached to the landingstring and wherein the clamp means further comprises a second set ofdies adapted to engage a slot located in the second floatation module.In the preferred embodiment, the first shell comprises a latching rodand the second shell comprises a latching protrusion and wherein thelatching rod is configured to engage the latching protrusion in order tolatch the first shell and the second shell together.

A method of landing a tubular string, such as casing or productionequipment, into a sub-sea well head from a floating drilling rig onto asub-sea well head is also disclosed, wherein a marine riser connects therig to the sub-sea well head. In the preferred embodiment, the tubularstring is a casing string. The method comprises running the casingstring into the marine riser, and connecting a casing hanger to thecasing string. Next, a landing string is attached to the casing hanger.A floatation module is connected to the landing string.

The method further includes lowering the landing string through themarine riser so that the weight of the tubular string being lowered intothe marine riser is reduced. The casing hanger can then be landed intothe sub-sea well head.

In one preferred embodiment, the floatation module comprises a tubularmember having a buoyant material bonded thereto, a slot formed withinthe tubular member, and engagement means for engaging with the slot andthe step of attaching the floatation module to the landing stringincludes attaching the engagement means with the slot in order to clampthe floatation module with the landing string. Also, the engagementmeans may comprise a die member and wherein the step of attaching theengagement means further includes engaging the die member into the slot.

An advantage of the present invention includes an apparatus and methodthat safely reduces rig hoisting requirements. Another advantage is thatthe invention is safer than prior art methods and devices. Yet anotheradvantage is that an operator can install floatation modules beforegoing to the rig site, or can install at the rig site. Another advantageis the modularity of the invention. For instance, an operator caninstall several floatation modules per joint of pipe, or alternatively,the operator can space out floatation modules in a predeterminedsequence along the entire length of the landing string in order toeffect the desired amount of buoyancy.

A feature of the invention is that the buoyancy material, such assyntactic foam, is bonded to a sleeve, such as an aluminum sleeve.Another feature is that the sleeve consist of two cylindrical halvesthat are latched together to form the floatation module. A feature isthe clamp means for clamping the halves together. Yet another feature isthat the sleeve can contain engagement means that comprises slots.Another feature is that the clamp means includes dies that engage withthe slots thereby holding the sleeves about the landing string.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of the floatation module of the presentinvention in the open position.

FIG. 2 is an isometric view of the clamp means of the present inventionin the open position.

FIG. 3 is an isometric view of the clamp means seen in FIG. 2, with theclamp means in the closed position.

FIG. 4 is an isometric exploded view of the floatation modules about ajoint of landing string.

FIG. 5 is an isometric assembled view of the floatation modules of FIG.4 shown clamped about a joint of the land string.

FIG. 6 is a schematic view of the floating platform lowering a tubularstring into a well in accordance with the teachings of the presentinvention.

FIG. 7 is a sequential schematic view of the floating platform seen inFIG. 6 wherein the tubular string has been lowered to a predetermineddepth.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an isometric view of the floatation module 2 of thepresent invention in the open position will now be described. As seen inFIG. 1, the floatation module 2 contains a first half cylindrical sleeve4 and a second half cylindrical sleeve 6. A cylindrical member is formedwhen the first half cylindrical sleeve 4 and second half cylindricalsleeve are joined together. In the most preferred embodiment, the firsthalf tubular sleeve 4 and the second half tubular sleeve 6 areconstructed of aluminum.

A buoyant material will be bonded to the first half cylindrical sleeve 4and the second half cylindrical sleeve 6. In the most preferredembodiment, the buoyant material is a syntactic foam commerciallyavailable from CRP Corporation under the name Syntactic Foam. Forinstance, the bonded foam, which is bonded to the sleeve 4, is seengenerally at 7.

FIG. 1 also shows that the first half cylindrical sleeve 4 has means forengaging with a clamp, wherein the clamp will be explained withreference to FIG. 2. Returning to FIG. 1, for the first half cylindricalsleeve 4, the engaging means includes slot 10 formed on a first end ofthe first half cylindrical sleeve 4, and the slot 14 formed on a secondend of the first half cylindrical sleeve 6. For the second halfcylindrical sleeve 6, the engaging means includes slot 18 on a first endof the second half cylindrical sleeve 6, and the slot 20 formed on thesecond end of the second half cylindrical sleeve 6. In the mostpreferred embodiments, the slots are rectangular in shape. FIG. 1 alsoshows a third half cylindrical sleeve 22 and a fourth half cylindricalsleeve 23.

Referring now to FIG. 2, an isometric view of the clamp means 24 of thepresent invention in the open position is shown. The clamp means 24contains a first half cylindrical shell 26 and a second half cylindricalshell 28 that pivotly attached via the hinge means 30. In the preferredembodiment shown in FIG. 2, the hinge means 30 is a conventional type ofhinge having a rod 31 extending through cylindrical bodies.

FIG. 2 also depicts that the clamp means 24, and in particular themember 26, contains a first die 32 and a second longitudinally spaceddie 34, wherein the dies are protrusions fixed on the inner portion ofthe shell 26. The shell 28 contains the third die 36 and a fourthlongitudinally spaced die 38, wherein the dies are protrusions fixed onthe inner portion of the member 28. In the most preferred embodiment,the dies are rectangular, formed on the inner portion of the shells 26,28, and are configured to engage the slots formed on the sleeves of thefloatation modules.

FIG. 2 also shows a pair of mounting brackets, namely mounting bracket40 and mounting bracket 42. The mounting brackets 40, 42 will have rods44, 46, respectively, that are pinned to the mounting brackets 40, 42.The rod 44 is configured to cooperate and engage with the receivingbracket 48, wherein the receiving bracket 48 is attached to the firsthalf shell 26. The receiving bracket 48 has the cavity 48 a configuredto receive the rod 44. The rod 46 is configured to cooperate and engagewith the receiving bracket 50, wherein the receiving bracket 50 isattached to the first half cylindrical member 26. The receiving bracket50 has the cavity 50 a configured to receive the rod 46. The rod 44 willhave nut member 52 that will engage external thread means on the rod 44,wherein the nut member 52 will fasten the members 26, 28 together. Also,the rod 46 will have nut member 54 that will engage external threadmeans on the rod 46, wherein the nut member 54 will fasten the members26, 28 together.

Referring now to FIG. 3, an isometric view of the clamp means 24 seen inFIG. 2, with the clamp means 24 being in the closed position will now bedescribed. It should be noted that like numbers appearing in the variousfigures will refer to like components. The members 26, 28 have beenpivoted closed via the hinge 30. The rod 44 pivots to engage thereceiving bracket 48 within cavity 48 a, and the rod 46 pivots to engagethe receiving bracket 50 within cavity 50 a. The nut members 52, 54 canthen be turned to fasten the clamp means 24.

FIG. 4 is an isometric exploded view of a plurality of floatationmodules about a joint of landing string 62. More specifically, FIG. 4shows a first floatation module 64 that consist of a first half sleeve64 a and a second half sleeve 64 b; a second floatation module 66 thatconsist of a first half sleeve 66 a and a second half sleeve 66 b; and,a third floatation module 68 that consist of a first half sleeve 68 aand a second half sleeve 68 b. The sleeve 64 a has slots 70, 72; thesleeve 64 b has slots 74, 76; the sleeve 66 a has slots 78, 80; thesleeve 66 b has slots 82, 84; the sleeve 68 a has slots 86, 88; and, thesleeve 68 b has slots 90, 92. In the most preferred embodiment, thesleeves 64 a, 64 b, 66 a, 66 b, 68 a, and 68 b comprise the aluminumsleeve with the bonded foam, as previously described.

Also shown in FIG. 4 are the clamp means. The clamp means 94 will engagethe floatation module 64, and in particular, the slots 70, 74 via thedies of clamp means 94. The clamp means 96 will engage the floatationmodules 64 and 66, and in particular, the slots 72, 76 and slots 78, 82via the dies of clamp means 96. The clamp means 98 will engagefloatation modules 66 and 68, and in particular, the slots 80, 84 andslots 86, 90 via the dies of clamp means 98. The clamp means 100 willengage the floatation module 68, and in particular the slots 88, 92 viathe dies of clamp means 100.

The landing string 62 has box end 104 and a pin end 106. It should benoted that while three floatation modules have been shown, the actualnumber placed per joint can vary. In fact, with some landing strings, itis possible to alternate the placement of the floatation modules amongstvarious joints. The actual number, length of the floatation modules,thickness of the buoyant material, etc. will depend on specific designcriteria. Many design criteria can be considered, such as the amountweight reduction required, rig space, etc.

Referring now to FIG. 5, an isometric assembled view of the floatationmodules of FIG. 4 shown clamped about a joint of the landing string 62will now be described. More specifically, the floatation module 64 hasbeen engaged to the landing string 62 via the clamp means 94 and clampmeans 96. The floatation module 66 has been engaged to the landingstring 62 via the clamp means 96 and clamp means 98. The floatationmodule 68 has been engaged to the landing string 62 via the clamp means98 and clamp means 100. Hence, the buoyant landing string 62, as seen inFIG. 5, and can now be run into the marine riser using convention meansknown to those of ordinary skill in the art.

In FIG. 6, a schematic view of a floating platform 110 lowering atubular string 112 into a well 114 in accordance with the teachings ofthe present invention will now be described. FIG. 6 shows a surfacecasing 115 already cemented into place in the earth's surface, asunderstood by those of ordinary skill in the art. The tubular string 112being lowered, in one preferred embodiment, will be a casing string 112,and the floating platform 110 will contain a drilling rig 116. Thedrilling rig 116 will contain a hoisting system that includes the block118. A sub-sea well head 120 is position on the ocean floor, and whereina marine riser 122 extends from the sub-sea well head 120 on the oceanfloor to the floating platform 110. It should be noted that the tubularstring 112 can also be, in one embodiment, a production assembly forproducing hydrocarbons or a testing assembly for testing the well.

The method of landing a casing string 112 into a sub-sea well head 120from the floating platform 110 includes running the casing string 112into the marine riser 122 and connecting a casing hanger 124 to thecasing string 112. A casing hanger 124 is a device that serves to landand anchor to the casing string inside the sub-sea well head 120. Casinghangers are commercially available from FMC Inc. under the name casinghangers.

The method further includes attaching the landing string 126 to thecasing hanger 124. As noted earlier, the landing string 126 is a tubularmember that is used to lower into proper position a down hole component,and wherein the down hole component may be a casing string, bottom holeassembly containing a measurement while drilling tool with bit and mudmotor, production and testing assemblies, etc. The landing string 126may be referred to sometimes as a work string. In some embodiments, thelanding string 126 is a specially designed and/or sized drill pipe.

The method includes connecting a buoyancy module, such as the floatationmodules 64, 66 and 68 noted in FIG. 4, to the landing string 126. Theoperator would thereafter lower the landing string 126 (containing thefloatation modules) through the marine riser 122. Since the marine riser122 will have a fluid therein, the weight of the tubular string 112being lowered into the marine riser 122 will be reduced, according tothe teachings of this invention. Next, and as seen in FIG. 7, the casinghanger 124 can be landed into the sub-sea well head 120. A plurality offloatation modules, including 130, 132, 134, 136, are shown clampedabout the landing string 126. Hence, the casing string 112 has beenlowered to a predetermined depth safely by reducing the rig hoistingrequirements.

Although the present invention has been described in terms of specificembodiments, it is anticipated that alterations and modificationsthereof will no doubt become apparent to those skilled in the art. It istherefore intended that the following claims be interpreted as coveringall such alterations and modifications as fall within the true spiritand scope of the invention.

1. An apparatus for reducing the load applied to a rig, the rig beingpositioned over, with the well having a tubular string disposed therein,the apparatus comprising: a landing string connected to the tubularstring; a first floatation module attached to the landing string; clampmeans for clamping the first floatation module onto the landing string.2. The apparatus of claim 1 wherein said first floatation modulecomprises a tubular sleeve having buoyant material applied thereto. 3.The apparatus of claim 2 further comprising a first plurality of slotsformed in the tubular sleeve that engage with the clamp means.
 4. Theapparatus of claim 3 wherein said tubular string is a casing string. 5.The apparatus of claim 4 wherein said tubular sleeve is constructed ofaluminum and said buoyant material comprises a foam bonded to saidaluminum sleeve.
 6. The apparatus of claim 5 wherein said tubular sleevecomprises a first cylindrical half body and a second cylindrical halfbody.
 7. The apparatus of claim 6 wherein said clamp means comprises afirst shell attached to a second shell, and wherein said first shell andsaid second shell are pivotly attached to form a cylindrical memberhaving an internal portion.
 8. The apparatus of claim 7 wherein saidclamp means further comprises a first set of dies adapted on theinternal portion of said cylindrical member in order to engage the firstplurality of slots formed in the tubular sleeve.
 9. The apparatus ofclaim 8 wherein a second floatation module is attached to said landingstring and wherein said clamp means further comprises a second set ofdies adapted on the internal portion of said cylindrical member in orderto engage a second plurality of slots located in said second floatationmodule.
 10. The apparatus of claim 9 wherein said first shell comprisesa latching rod and said second shell comprises a latching protrusion andwherein said latching rod is configured to engage said latchingprotrusion in order to latch said first shell and said second shelltogether.
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